The present invention relates to an apparatus for the transmission of power from a source to a load and, more particularly, to a flywheel electric transmission system which may be advantageously, although not exclusively, employed for vehicular propulsion.
In an attempt to conserve energy and reduce air pollution, various alternatives to the use of conventional internal combustion automotive engines have been proposed. Among these alternatives, systems commonly known as hybrids have been suggested. Some hybrid systems incorporate a battery pack for supplying power during short-trip driving and a fuel burning engine for longer trips. Other types of hybrid systems combine a relatively low power prime mover or engine with an energy storage device, such as a flywheel, for supplementing the power output of the engine in situations where the load (the wheels of the vehicle) requires more power or torque. Still other types combine a battery pack and an energy storage device. Thus, in a hybrid system where the engine power is sufficient for cruising on level roads, supplemental power may be required for going up grades, for quick acceleration and the like. This additional power is supplied from the flywheel in the form of kinetic energy which would have been stored therein during periods where the engine was delivering more power than required, such as during periods of driving on a down grade, of braking and the like.
Heretofore, these hybrid systems comprised essentially: a prime mover or engine developing a mechanical power output; a generator for converting such mechanical power to electrical power; an energy storage device such as a flywheel or battery; a load such as wheels; and at least two motor/generator devices for transmitting power to or receiving power from the flywheel or batteries and the load. At each point where power is converted from one form to another (mechanical to electrical and vice versa) conventional conversion circuits are required for matching voltages or frequencies, as is well known. Losses in overall power and efficiency result at each point where power is converted in the motors, generators or conversion circuits. Thus the multiple power conversions of these types of hybrid systems create losses which cumulatively affect the ability of the system to perform efficiently.
In addition to the multiple conversion losses in power, such hybrid systems suffer from weight losses in that each employs at least three relatively large sized separate electric machines and energy storage means thereby adding to the bulk and overall cost of a system.